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Conformational Spread as a Mechanism for Cooperativity in the Bacterial Flagellar Switch

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Science  05 Feb 2010:
Vol. 327, Issue 5966, pp. 685-689
DOI: 10.1126/science.1182105

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Abstract

The bacterial flagellar switch that controls the direction of flagellar rotation during chemotaxis has a highly cooperative response. This has previously been understood in terms of the classic two-state, concerted model of allosteric regulation. Here, we used high-resolution optical microscopy to observe switching of single motors and uncover the stochastic multistate nature of the switch. Our observations are in detailed quantitative agreement with a recent general model of allosteric cooperativity that exhibits conformational spread—the stochastic growth and shrinkage of domains of adjacent subunits sharing a particular conformational state. We expect that conformational spread will be important in explaining cooperativity in other large signaling complexes.

  • * These authors contributed equally to this work.

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